Book resources for learning Ruby on Rails

Sure, you can access nearly everything you need to learn RoR online but I am personally still addicted to the dead-tree model of learning. If you are like me and prefer buying books then read on. In the last year I've bought 10 books on various Ruby/Rails topics and what follows are the ones I've gotten the most use out of.
NOTE: Ruby on Rails is a constantly evolving environment and the information below is really relevant for early June 2009. Things can change in the Rails world relatively quickly. It's a good idea to stay up on Rails developments by following the Ruby on Rails blog at a minimum.
Learn Ruby First
Before you rush out to buy a Ruby on Rails specific book first you need to learn Ruby the programming language. If you've been writing applications in C/C++/C#/Pascal (like I had) then Ruby is a relatively easy language to learn. Since it is open source getting a copy of Ruby is usually just a matter of downloading it to your machine and running it. Mac users have a big advantage here because Ruby is bundled in with Leopard.
Though you can get up and running with Rails while having a very modest knowledge of Ruby I can't stress enough that you should take the time to understand Ruby before you dive into Rails. Why? Because building a basic application with Rails is so easy that you will be tempted (as I did) to just start building. If you haven't really learned the Ruby language you will take a lot for granted and not understand why things work the way they do. You will copy and paste code rather than write it and when you do write it you will likely not write it well.

If you want to become adept at using Rails you do not need to read the book cover to cover but should get through Part I before you start doing anything of significance.

Both of these books are excellent resources for learning about the Ruby language and I recommend having them in your library.
Rails References
Once you have got a good grasp on the Ruby language you can dive into Rails. Once again I have two books that I turn to frequently. One is for learning/getting started, the other is a desktop reference.

The authors use a step-by-step style to build up an online bookstore, providing side roads and discussion points along the way. Some of the core philosophies of Rails are mentioned here (like DRY), though they don't go into a lot of detail. I personally found that good; what I was looking for was a relatively light-weight book that takes me quickly through building an application so that I could see results. AWDR does that and starts to show off some of the cool things you can do in a Rails application.

Obie has created a great desktop reference that you can pick up and dive in at just about any point. You don't read The Rails Way cover to cover; you keep it handy and pop it open when you need to know more about something you're working on.
So there you have it, four great books on Ruby and Rails that will help you get started building applications in that environment. As I said at the beginning, Rails is a rapidly evolving environment and it's difficult for books to keep up.
Got a book for Ruby or Rails that you really like? A web site with excellent tutorials? Please drop a note in the comments and share.
Comments
Best (free) Rails podcast: http://railsenvy.com
@akmassey: Thanks - those are both excellent resources.
As for the selection of RoR over Python, Java, etc. I really wanted to go with a framework that was simple, something I could grok pretty quickly. The reason I was tired of Visual Studio was the sheer complexity of the environment; when you have a development tool that can target anything from custom client applications and command line utilities on through web based services you have a huge amount of overlap.
Though Java has a huge following I didn't really give it too much thought. Most of the folks I knew that developed in Java didn't seem to care for it. For that reason more than anything else I didn't really consider it.
I did look very briefly at Python but didn't find that the frameworks (Django in particular) were as mature or comprehensive as RoR was. If I was going to switch to a new open source based language I wanted one that was in heavy use and had a vibrant and active community.
Keep in mind that my selection process was for an entrepreneur using this for my own business. If you are doing this to help build up your resume for either job growth or to obtain additional contracts your criteria would be very different than mine.